1. Field of the Present Invention
The present invention relates to an illumination light source device, a projection device including the illumination light source device and an improved method to control the projection device.
2. Description of the Related Art
Conventionally, light source devices employing a high-intensity discharge lamp such as an extra high pressure mercury lamp, as illumination light source devices for projection devices (projector) projecting on-screen information of a personal computer (hereinafter referred to as “PC”) at conferences and meetings have been known.
However, the discharge lamp takes a necessary time to emit light stably after start of lighting, while enables high-brightness at low cost.
Then, using a solid-state light-emitting element such as a light-emitting diode or an organic light emitting diode of red (R), green (G), and blue (B) as an alternate light source in place of the discharge lamp has been proposed and put into practical use.
By using the solid-state light-emitting element as a light source for a projector, the projector can be started-up quickly and can be configured to accomplish a care of environment.
Then, for example, Japanese Patent Application Publication No. 2011-013316 (Patent Document 1) and Japanese Patent Application Publication No. 2010-085745 (Patent Document 2) were developed to solve the problem mentioned above.
As the illumination light source device employing the solid-state light-emitting element, for example, it is widely known that the skill to obtain a colored projection image by irradiating a fluorescent body with laser light as a excitation light emitted by a blue laser diode used as a first light source (excitation light source), producing each light of R, G, and B by exiting the fluorescent body, and controlling gradation each light of R, G, and B by use of a light modulation device such as a DMD (Digital Micromirror Device)(refer to Patent Document 1).
An illumination light source device according to Patent Document 1 includes a luminescent plate (fluorescent wheel) composed of a fluorescent body layer having a plurality of segmented regions divided in a rotational direction and emitting fluorescent light by receiving excitation light and a transmission region transmitting the excitation light directly, a first light source irradiating the fluorescent body with the excitation light, a second light source emitting light of a different wavelength from both of the excitation light and the fluorescence emitted by the fluorescent body layer, a light collection optical system collecting light emitted by the luminescent plate (fluorescent wheel) and the light emitted by the second light source on the same light-path, and an emission control section controlling the first light source and the second light source.
The emission control section turns off the first light source not to emit a light by the first light source and turn on the second light source to emit a light by the second light source, in order to prevent a color mixture at a boundary of adjacent segmented regions.
The illumination light source device according to Patent Document 1 can prevent the color mixture at the boundary of the adjacent segmented regions by being configured to control to turn off the first light source at the boundary. However, a time period that the segmented region is irradiated with the excitation light per unit time (one second) is constant regardless of its revolutions of the fluorescent wheel per unit time (one second), since the illumination light source device is configured so that the fluorescent body of the fluorescent wheel is directly irradiated with the excitation light. Therefore, a fluorescence property of the fluorescent body may be deteriorated if a mini-region of the segmented region remains irradiated with the excitation light.
Now, there are being developed illumination light source devices capable of keeping the fluorescent property of the fluorescent body from deteriorating by enabling the fluorescent body to change the time that being irradiated with the excitation light in unit time by providing a reflection-transmission wheel as a reflection-transmission member having a transmission region and the reflection region on a light-path of the excitation light emitted by the first light source, providing a fluorescent wheel as a fluorescent member on at least one of a transmission light-path made of the transmission region and a reflection light-path made of the reflection region, and switching the light-path of the excitation light between the transmission light-path and the reflection light-path in an unit time (one second) of rotation of the fluorescent wheel.
However, a color mixture occurs when the reflection-transmission wheel is irradiated with the excitation light while a boundary region between the reflection region and the transmission region is passing through, even if the illumination light source device is configured so that the reflection-transmission wheel is provided on the light-path of the excitation light emitted by the first light source.
Moreover, to prevent the color mixture, turning off an excitation light source while the boundary region between the reflection region and the transmission region is passing through the light-path of the excitation light is one idea. But, such a configuration to turn off the excitation light source decreases the brightness.